Resist polymer and chemical amplified resist composition containing the same

ABSTRACT

A copolymer represented by the formula I and a chemical amplification resist containing the copolymer, which can be easily controlled in sensitivity by regulating the content and kind of the norbornene derivatives in the matrix polymers in addition to being superior in adherence to substrate and dry etch resistance: ##STR1## wherein, X is selected from the group consisting of the following general formulas II, III and IV; and, l, m, n and o each are a repeating number not more than 0.5, satisfying the condition that l+m+n+o=1 and 0.4≦o≦0.5: ##STR2##

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a chemical amplification resistcopolymer and a resist composition containing it. More particularly, thepresent invention relates to a photoresist copolymer, which is useful asa matrix resin to form micro patterns, and a chemical amplificationresist composition based on the copolymer, which makes it possible toperform a sub-micro lithography process using a deep UV such as a KrFexcimer laser or an ArF excimer laser, an X ray such as synchrotronradiation, or charged particle beams such as electron beams.

2. Description of the Prior Art

Certainly, the recent thrust into the high integration of semiconductordevices is greatly based on advances in microlithography. For example,ultra-fine patterns as small as sub-microns, e.g. 0.2 microns or less,in size, are required for the fabrication of ultra-LSI. Now, the lightsources used to form the fine patterns become increasingly shorter inwavelength, for example, from g-line or i-line, to deep UV light,including KrF excimer lasers and ArF excimer lasers, further to X-rays,and finally to electron beams.

With near UV light, such as g-line or i-line, which is used inconventional lithography, micro patterns as small as quarter microns(0.25 microns) are virtually impossible to realize. Such a micro patternrequires shorter wavelengths which belong to deep UV excimer lasers, Xrays, and electron beams. Of them, KrF and ArF excimer lasers occupiedthe attention of the researchers in expressing such exquisiteness, andwere developed as a light source, requiring novel photoresists. Now,chemical amplification photoresists are prevalently used for deep UVlight.

A chemical amplification resist composition suitable for deep UV lightfundamentally comprises a polymer with an acid-dissociable functionalgroup, a compound which generates an acid (hereinafter referred to as"photoacid generator"), and a solvent, and avails itself of chemicalamplification effect in lithography.

Most of the chemical amplification resists used for KrF excimer lasersare based on phenolic resins which, however, are found to be unsuitablefor utilizing an ArF excimer laser because their aromatic rings absorbthe light.

As an alternative, polyacrylate derivatives appeared to avoid suchabsorption. Polyacrylate derivatives show little absorbance at 193 nm,but suffer from a great disadvantage in that they are far inferior indry etch resistance. Recently, much effort has been made to overcome thedisadvantage, including the introduction of alicyclic derivatives intopolyacrylate. The introduction of alicyclic derivatives certainly bringsabout an improvement in dry etch resistance, but causes a significantproblem in a developing process because their hydrophobicity has anegative influence on the affinity for developing solutions.

It is known that copolymers of maleic anhydride and olefin can be usedas matrix resins which show not only hydrophilicity, but also etchresistance. In the copolymers, maleic anhydride, responsible forhydrophilicity, serves as a promoter which enables the copolymerizationwith olefinic monomers to be accomplished at low temperatures at lowpressures.

SUMMARY OF THE INVENTION

With the background in mind, the present inventors repeated researchintensively and thoroughly, aiming to develop a base resin forphotoresist, and resulted in the finding that hydroxy-containingnorbornene derivative monomers and maleic anhydride monomers give agreat contribution to their polymers in improving adherence tosubstrate, transparency to deep UV light, and dry etch resistance aswell as photosensitivity, resolution and developability.

Therefore, it is an object of the present invention to provide acopolymer as a base resin for photoresist, with which there can beobtained patterns as fine as 0.2 μm .

It is another object of the present invention to provide a chemicalamplification positive photoresist composition containing the resin.

DETAILED DESCRIPTION OF THE INVENTION

In order to obtain patterns as fine as 0.2 microns by use of light asshort in wavelength as ArF excimer laser, new chemical amplificationresists have been being actively developed because previous ones did notgive desirable patterns. For example, polyhydroxystyrene-based resistsshow a large absorbance at the wavelength of the light source (193 nm).

In forming 0.2 micron or less patterns, the adherence of a resistcomposition to a substrate plays an important role. Carboxylic acid wasintroduced into the side chains of matrix polymers for the purpose ofincreasing the adherence. Carboxylic acid-grafted matrix polymers,however, require a change in the basicity of developing solutionsbecause the existence of carboxylic acid alters the solubility of thematrix polymers in the aqueous alkaline solutions.

In the polymer according to the present invention, a hydroxy-containingnorbornene derivative is introduced into its main chain with the aim ofcontrolling the adherence to substrates and the solubility in aqueousalkaline solutions while a cyclic group exists as a member of its mainchain to enhance dry etch resistance.

Accordingly, the present invention provides a polymer for chemicalamplification resist, having a repeating unit which comprises anorbornene moiety and a maleic anhydride moiety, and a chemicalamplification resist composition based on the polymer.

More details are given of the present invention, below.

POLYMER

The polymer useful in the present invention has a repeat unit consistingof a norbornene, norbornene derivatives and a maleic anhydride. Thepolymer itself is insoluble or hard-soluble in aqueous alkalinesolutions and contains at least one protecting group which can bedissociated by acid.

The alkali solubility of the polymer is primarily dependent on thecontent of the acid functional groups which are dissociable by acid.Accordingly, the resist properties of the polymer, including adherenceto substrate, photo-sensitivity, resolution and the like, can bedetermined by the kind and quantity of the norbornene derivatives usedin the polymer.

The polymer of the present invention is a multi-membered copolymerrepresented by the following general formula I: ##STR3## wherein,

X is selected from the group consisting of the following generalformulas II, III and IV: ##STR4## wherein R₁ is selected from the groupconsisting of straight or branched alkyl groups, cyclic or polycyclicalkyl groups, alkyl carbonyl groups, branched alkyl carbonyl groups, andcyclic or polycyclic alkyl carbonyl groups, all containing 1-10 carbonatoms, which are exemplified by acetyl, t-butyl oxycarbonyl, cyclohexanecarbonyl, adamantane carbonyl, bicyclo[2,2,1]heptane methyl carbonyl andthe like; R₂, R₃ and R₄ are independently selected from the groupconsisting of straight or branched alkyl groups, and cyclic orpolycyclic alkyl groups, all containing 1-10 carbon atoms, which areexemplified by methyl, ethyl, t-butyl, iso-propyl, adamantyl,bicyclo[2,2,1]heptane methyl and the like; and

l, m, n and o each are a repeating number not more than 0.5, satisfyingthe condition that l+m+n+o=1 and 0.4≦o≦0.5. The resist properties, suchas adherence to substrate, photosensitivity and resolution, are takeninto account in determining the repeating numbers, l, m and n.

When the X moiety reveals itself in the general formula I, the repeatunit of the polymer is represented by the following general formulas V,VI and VII: ##STR5##

The repeating unit of the Formula I can be prepared by polymerizing anacid-dissociable functional group containing norbornene derivativesselected from the general formulas II, III and IV, a maleic anhydriderepresented by the following structural formula VIII, a norbornene ofthe following structural formula IX, and3-bicyclo[2,2,1]hept-5-en-2-yl-3-hydroxy-propionic acid t-butyl ester(hereinafter referred to as "BHP") represented by the followingstructural formula X, in the presence of a polymerization catalyst.##STR6## Account must be taken of the adherence to substrate whendetermining the amount of the BHP monomer represented by the structuralformula X.

These multi-membered polymers may be in the form of a block copolymer, arandom copolymer or a graft copolymer. They may be prepared inconventional polymerization processes and, preferably by the action of aradical initiator. For this radical polymerization, an availableinitiator may be azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO),lauryl peroxide, azobisisocapronitrile, azobisisovaleronitrile, ort-butylhydroperoxide, but is not specifically limited to them. Thepolymerization of the monomers may be carried out in a manner of bulkpolymerization, solution polymerization, suspension polymerization,bulk-suspension polymerization or emulsion polymerization. Examples ofuseful polymerization solvents include benzene, toluene, xylene,halogenobenzene, diethylether, tetrahydrofuran, acetates, esters,lactones, ketones, amides and mixtures thereof.

The temperature of the polymerization is dependent on the polymerizationcatalyst employed. For example, if azobisisobutyronitrile is used as apolymerization catalyst, the polymerization is preferably carried out ata temperature of about 60-90° C.

As for the molecular weight of the polymer prepared, it can becontrolled by varying the amount of the polymerization initiator and theperiod of polymerization time. After completion of the polymerization,the monomer residues which remain unreacted in the reaction mixture, andby-products are preferably removed by solvent precipitation. The polymerof the Formula I preferably has a polystyrene-reduced average molecularweight (hereinafter abbreviated to "M_(w) ") ranging from about 1,000 to100,000 as measured by gel permeation chromatography (GPC) and morepreferably from about 3,000 to 50,000 when taking into account thesensitivity, developability, coatability and thermal resistance whichare required for a photoresist. For example, if the polymer has an M_(w)of less than 1,000, the resulting photoresist composition is very poorin coatability and developability. On the other hand, if the Mw exceeds100,000, degradation occurs in sensitivity, resolution anddevelopability. In molecular weight distribution (Mw/Mn), the polymer ofthe invention preferably ranges from 1.0 to 5.0 and more preferably from1.0 to 2.0.

As mentioned above, the molecular weights and molecular weightdistributions of the polymers obtained were measured by use of GPC inthe model HLC-8020 manufactured by TOSHO, equipped with columnsG2000HXL, G3000HXL and G4000HXL, eluting tetrahydrofuran at a flow rateof 1.0 ml/min at a column temperature of 40° C. with a standard ofmono-dispersed polystyrene.

In the present invention, only one or a mixture of the polymers obtainedmay be used for the resist.

PHOTOACID GENERATOR

Photoresist patterns as fine as 0.2 microns can be usefully formed byuse of the polymers of the present invention. Therefore, the presentinvention also pertains to a chemical amplification photoresistcomposition comprising the polymer and a photoacid generator.

As the photoacid generator useful in the present invention, an oniumsalt, such as iodonium, sulfonium, phosphonium, diazonium andpyridonium, will suffice. Concrete, particularly effective, butnon-limitative examples of the onium salt include triphenylsulfoniumtriflate, diphenyl(4-methylphenyl)sulfonium triflate,diphenyl(4-t-butylphenyl)sulfonium triflate,diphenyl(4-methoxyphenyl)sulfonium triflate, dibutyl(naphthalen-1-yl)sulfonium trif late, triphenylsulonium hexafluoroantimonate,diphenyliodonium triflate, diphenyliodonium methylbenzenesulfonate,bis(cyclohexylsulonyl)diazomethane, andbis(2,4-dimethylphenylsulfonyl)diazomethane. A halogen compound also canbe used as the photoacid generator, which is exemplified by1,1-bis(4-chlorophenyl)-2,2,2-tricholorethane,phenyl-bis(trichloromethyl)-s-triazine ornaphthyl-bis(trichloromethyl)-s-triazine. Besides, diazoketonecompounds, such as 1,3-diketo-2-diazo, diazobenzoquinone anddiazonaphthoquinone, sulfonic compounds, sulfonic acid compounds, andnitrobenzyl compounds may be candidates for the photoacid generator.More preferable are the onium compounds and the diazoketone compounds.The photoacid generators may be used, singly or in combinations.

In contrast to common photoacid generators, the onium salts representedby the following general formulas XI and XII not only serve asdissolution preventers in unexposed areas, but act to promotedissolution in exposed areas: ##STR7## wherein R₁ and R₂, which may bethe same or different, each represents an alkyl, an allyl or an aryl; R₃and R₄ which may be the same or different, each represents a hydrogenatom, an alkyl or an alkoxy; and n is an integer of 0-14.

The photoacid generators are used at an amount of approximately 0.1-30parts by weight based on 100 parts by weight of the solid content of thephotoresist composition, and preferably at an amount of 0.3-10 parts byweight. They may be used alone or in mixture of at least two species.

In the present invention, if necessary, there may be used a compoundwhich is decomposed by acid to promote the dissolution of thephotoresist in a developing solution. As such an acid-decomposable anddissolution-promoting function group, t-butyl ester is most suitable.Therefore, alicyclic derivatives containing t-butyl ester may berecruited in the present invention. Upon formulation, they may be addedat an amount of approximately 3-60 parts by weight based on 100 parts byweight of the solid content of the photoresist composition, andpreferably approximately 5-40 parts by weight.

Optionally, the photoresist composition of the present invention maycomprise additives, such as a surfactant, an azo compound, a halationinhibitor, an adhesive aid, a preservation stabilizer, an antifoamingagent and the like. As for surfactant, it may be exemplified bypolyoxylauryl ether, polyoxystearyl ether, polyoxyethylene oleyl ether,polyethyleneglycol dilaurylate, etc. The surfactant is preferably usedat an amount of 2 parts by weight or less based on 100 parts by weightof the solid content of the photoresist composition.

When being exposed to light, the photoacid generator, as implied in itsname, generates acid. Because the acid plays a great role in determiningthe sensitivity of the photoresist, it is needed to prevent itsdiffusing. For this purpose, a base additive may be used. Useful areamine or ammonium compounds. It is preferable that the base compound isused at an amount of approximately 0.01-5 parts by weight based on thetotal solid content. For example, if the base compound is added at anamount more than the upper limit, the diffusion of the acid is reduced,but the sensitivity is lowered.

To obtain a uniform and flat photoresist coating, the solvent used isrequired to show an appropriate evaporation rate and viscosity. Examplesof such a solvent include ethyleneglycol monomethyl ether,ethyleneglycol monoethyl ether, ethyleneglycol monopropyl ether,methylcellosolve acetate, ethylcellosolve acetate, propyleneglycolmonomethyl ether acetate, propyleneglycol monoethyl ether acetate,propyleneglycol monopropyl ether acetate, methylethyl ketone,cyclohexanone, methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate,2-heptanone, ethyl lactate, and gamma-butyrolacetone. They, ifnecessary, may be used, alone or in combinations. Depending on itsphysical properties, such as volatility and viscosity, the solvent isused at such an appropriate amount that a uniform and flat photoresistcoating could be formed on a wafer.

A photoresist film is typically obtained by coating the photoresistsolution on a wafer and drying it. After being filtered, the photoresistsolution may be coated by use of a spin coating, flow coating or rollcoating technique.

Then, selective irradiation on the photoresist film coated is performedto give fine patterns. The available radiation, although it is notspecifically limited, may be UV light, such as I-line, deep UV light,such as KrF or ArF excimer lasers, X rays, or charged particle beams,such as electron beams, depending on the photoacid generator used.Following the radiation, a thermal treatment may be optionally done toimprove the sensitivity of the film.

Generally, the formation of photoresist pattern is finally completed ina developing solution. Examples of the developing solution includeaqueous solutions of sodium hydroxide, potassium hydroxide, sodiumcarbonate, sodium silicate, sodium metasilicate, ammonia water, ethylamine, n-propyl amine, triethyl amine, tetramethylammonium hydroxide andtetraethylammonium hydroxide with particular preference totetramethylammonium hydroxide. If necessary, additives, such assurfactants and aqueous alcohols, may be added.

A better understanding of the present invention may be obtained in lightof the following examples which are set forth to illustrate, but are notto be construed to limit the present invention.

SYNTHESIS OF MONOMERS SYNTHESIS EXAMPLE I

In a four-necked flask equipped with a stirrer and a reflux condenserwere placed 50 g of a Zn-Cu couple and 90 ml of tetrahydrofuran,followed by slowly charging a solution of 53 ml of t-butyl bromoacetateand 36 ml of 5-norbornen-2-carboxyaldehyde in 180 ml of tetrahydrofuran.After completion of the charging, the solution was subjected to refluxat 70° C. for 2 hours and then, cooled to room temperature. The Zn-Cucouple was filtered off, after which the solution was washed andextracted with the same solvent and distilled under vacuum to give 39 gof 3-bicyclo[2,2,1]hept-5-en-2-yl-3-hydroxy-propionic acid t-butyl ester(BHP) monomer, represented by the following structural formula M-I.##STR8##

SYNTHESIS EXAMPLE II

A solution of 50 g of BHP in methylene chloride was added with 20 g ofacetyl chloride at 0° C. and then, slowly with 32 g of triethyl amine.While the triethyl amine served as a reaction catalyst, the solution wasallowed to react by stirring for 1 hour at the same temperature, and thesolvent was removed by vacuum distillation. The reaction mixture dilutedin ether was washed with an aqueous sodium carbonate solution and thenwith brine. The organic layer thus formed was isolated and dried overmagnesium sulfate, and the complete removal of the solvent yielded 57 gof the monomer represented by the following structural formula M-II.##STR9##

SYNTHESIS EXAMPLE III

The procedure of Synthesis Example II was repeated using 37 g ofcyclohexanecarbonyl chloride instead of 20 g of acetyl chloride, toallow 66 g of the monomer represented by the following structuralformula M-III. ##STR10##

SYNTHESIS EXAMPLE IV

30 g of norbornene carboxylic acid dissolved in methylene chloride werecooled to 0° C. and added with 21 g of chloromethyl methyl ether andthen, added slowly with 28 g of triethyl amine. In the presence of thisbasic catalyst, the reactants were allowed to react by stirring for 1hour at the same temperature, and the solvent was removed by vacuumdistillation. The reaction mixture diluted in ether was washed with anaqueous sodium carbonate solution and then with brine. The organic layerthus formed was isolated and dried over magnesium sulfate, and thecomplete removal of the solvent yielded 35 g of the monomer representedby the following structural formula M-IV. ##STR11##

SYNTHESIS EXAMPLE V

The procedure of Synthesis Example IV was repeated using 24 g ofchloromethyl ethyl ether, instead of 21 g of chloromethyl methyl ether,to obtain 40 g of the monomer represented by the following formula M-V.##STR12##

SYNTHESIS EXAMPLE VI

67 g of cis-5-norbornen-endo-2,3-dicarboxylic anhydride and 50 g ofdiphenylaminopyridine were dissolved in 154 ml of t-butanol and stirredfor 15 hours at 80° C. After being neutralized with excess 5% aqueousHCl solution, the reaction mixture was extracted with ethyl acetate anddried over magnesium sulfate. Vacuum distillation was done to completelyremove the solvent, producing 91 g ofbicyclo[2,2,1]-5-hepten-2,3-dicarboxylic acid mono-t-butyl ester.

Thereafter, the procedure of the Synthesis Example IV was repeated using52 g of bicyclo[2,2,1]-5-hepten-2,3-dicarboxylic acid mono-t-butylester, instead of 30 g of norbornene carboxylic acid, to give 51 g ofthe monomer represented by the following structural formula M-VI.##STR13##

SYNTHESIS EXAMPLE VII

50 g of 5-norbornen-2,3-dicarboxyl anhydride and 47 g of isoborneol weredissolved in dimethyl acetamide and reacted at 80° C. for 15 hours inthe presence of 44 g of 4-dimethylaminopyridine while stirring. Aftercompletion of the reaction, the solution was cooled to room temperatureand neutralized with conc. hydrochloric acid. This neutralized reactionwas diluted in ethyl ether and washed three times with distilled water.The organic layer obtained was dried over magnesium sulfate and filteredto give 65 g of the compound represented by the following structuralformula C-I. ##STR14##

In dimethyl acetamide was dissolved 25.5 g of the compound (C-I) and tothis was added 7.7 g of chloromethyl methyl ether. After being cooled to0° C., the solution was slowly added with 12.1 g of triethyl amine withstirring and, then, subjected to reaction by stirring for 1 hour at thesame temperature. The reaction was diluted in ethyl ether and washedwith an aqueous Na₂ CO₃ solution and water. The organic layer formed wasisolated, dried over magnesium sulfate, and filtered to allow 25.2 g ofthe monomer represented by the following structural formula M-VII.##STR15##

SYNTHESIS EXAMPLE VIII

From the compound C-1, synthesized in Synthesis Example VII, 30.5 g ofthe monomer represented by the following structural formula M-VIII wereprepared in the same manner as that of Synthesis Example VII, exceptthat, instead of 7.7 g of chloromethyl methyl ether, 12.7 g of2-(chloromethoxymethyl)bicyclo[2,2,1]heptane were used. ##STR16##

SYNTHESIS EXAMPLE IX

5-norbornen-2,3-dicarboxylic acid was reacted in the same manner as thatof Synthesis Example VII, except for, instead of 47 g of isoborneol,37.9 g of 2-norbornane methanol were used, to give 64.4 g of thecompound represented by the following structural formula C-II.

From 23.2 g of this synthesized compound C-II, 20.7 g of the monomerM-IX, represented by the following formula M-IX, were obtained in thesame manner as that of Synthesis Example VII. ##STR17##

SYNTHESIS EXAMPLE X

From 26.8 g of the compound C-II synthesized in Synthesis Example IX,26.2 g of the monomer represented by the following structural formulaM-X were obtained in the same manner as that of Synthesis Example IX,except for, instead of 7.7 g of chloromethyl methyl ether, were used12.7 g of 2-(chloromethoxymethyl)bicyclo[2,2,1]heptane. ##STR18##

SYNTHESIS OF POLYMERS POLYMERIZATION EXAMPLE I

In a two-necked, round-bottomed flask equipped with a stirrer and areflux condenser, 2.38 g of the monomer M-I synthesized in SynthesisExample I, 5.61 g of the monomer M-II synthesized in Synthesis ExampleII, 4.90 g of maleic anhydride, and 1.88 g of norbornene were charged,together with 29.55 g of toluene and 0.82 g of AIBN. Under an argonatmosphere, the solution was well mixed by stirring for 2 hours at roomtemperature. Polymerization was initiated by activating the initiator at70° C. At 20 hours after the polymerization, the reaction was cooled toroom temperature. This polymerized solution was diluted withtetrahydrofuran and added to excess methanol/distilled water (4:1) togive precipitates. They were filtered and the filtrate was washedseveral times with the same mixed solvent and dried in vacuo to yield10.34 g of the polymer represented by the following structural formulaP1. It had a polystyrene-reduced weight average molecular weight ofabout 7,100. ##STR19##

POLYMERIZATION EXAMPLE II

The procedure of Polymerization Example I was repeated using 3.57 g ofthe monomer M-I, 5.23 g of the monomer M-III synthesized in SynthesisExample III, 4.90 g of maleic anhydride, 1.88 g of norbornene, togetherwith 0.82 g of AIBN as a polymerization initiator and 31.18 g of tolueneas a solvent, to allow 9.66 g of the polymer represented by thefollowing structural formula P2. This polymer was 6,200 inpolystyrene-reduced weight average molecular weight. ##STR20##

POLYMERIZATION EXAMPLE III

Polymerization was carried out in a similar manner to that ofPolymerization Example I, using 4.77 g of the monomer M-I, 1.82 g of themonomer M-IV synthesized in Synthesis Example IV, 4.90 g of maleicanhydride and 1.88 g of norbornene together with 0.82 g of AIBN and26.75 g of toluene, to allow 9.09 g of the polymer represented by thefollowing structural formula P3. This polymer was 6,600 inpolystyrene-reduced weight average molecular weight. ##STR21##

POLYMERIZATION EXAMPLE IV

4.77 g of the monomer M-I, 1.96 g of the monomer M-V synthesized inSynthesis Example V, 4.90 g of maleic anhydride and 1.88 g of norbornenewere polymerized in the presence of 0.82 g of AIBN in 27.03 g of toluenein a similar manner to that of Polymerization Example I, to allow 9.46 gof the polymer represented by the following structural formula P4, witha polystyrene-reduced weight average molecular weight of polymerrepresented by the following structural formula P4, with apolystyrene-reduced weight average molecular weight of 6,500. ##STR22##

POLYMERIZATION EXAMPLE V

2.38 g of the monomer M-I, 5.65 g of the monomer M-VI synthesized inSynthesis Example VI, 4.90 g of maleic anhydride and 1.88 g ofnorbornene were polymerized in the presence of 0.82 g of AIBN in 29.63 gof toluene in a similar manner to that of Polymerization Example I, toallow 9.77 g of the polymer represented by the following structuralformula P5, with a polystyrene-reduced weight average molecular weightof 5,800. ##STR23##

POLYMERIZATION EXAMPLE VI

In a two-necked, round-bottomed flask equipped with a stirrer and areflux condenser, 4.77 g of the monomer M-I synthesized in SynthesisExample I, 5.44 g of the monomer M-VII synthesized in Synthesis ExampleVII, 4.90 g of maleic anhydride, and 1.41 g of norbornene were charged,together with 0.49 of AIBN as a polymerization initiator and 33.04 g ofethyl acetate as a reaction solution. Under an argon atmosphere, thesolution was well mixed by stirring for 2 hours at room temperature.While maintaining the reaction temperature at 65° C., polymerization wascarried out for 20 hours. After completion of the polymerization, thereaction was cooled to room temperature. This polymerized solution wasdiluted with tetrahydrofuran and added in excess isopropyl alcohol, togive precipitates. They were filtered and the filtrate was washedseveral times with the same mixed solvent and dried in vacuo to yield11.06 g of the polymer represented by the following structural formulaP6. It had a polystyrene-reduced weight average molecular weight ofabout 6,800. ##STR24##

POLYMERIZATION EXAMPLE VII

4.77 g of the monomer M-I, 9.13 g of the monomer M-VIII synthesized inSynthesis Example VIII, 4.90 g of maleic anhydride and 0.94 g ofnorbornene were polymerized in the presence of 0.49 g of AIBN in 39.49 gof ethyl acetate in a similar manner to that of Polymerization ExampleVI, to allow 12.24 g of the polymer represented by the followingstructural formula P7, with a polystyrene-reduced weight averagemolecular weight of 5,700. ##STR25##

POLYMERIZATION EXAMPLE VIII

4.77 g of the monomer M-I, 5.02 g of the monomer M-IX synthesized inSynthesis Example IX, 4.90 g of maleic anhydride and 1.414 g ofnorbornene were polymerized in the presence of 0.49 g of AIBN in 32.20of ethyl acetate in a similar manner to that of Polymerization ExampleVI, to allow 10.95 g of the polymer represented by the followingstructural formula P8, with a polystyrene-reduced weight averagemolecular weight of 7,400. ##STR26##

POLYMERIZATION EXAMPLE IX

4.77 g of the monomer M-I, 8.57 g of the monomer M-X synthesized inSynthesis Example X, 4.90 g of maleic anhydride and 0.94 g of norbornenewere polymerized in the presence of 0.49 g of AIBN in 38.36 g of ethylacetate by following the process shown in Polymerization Example VI, toallow 12.08 g of the polymer represented by the following structuralformula P9, which was 6,200 in polystyrene-reduced weight averagemolecular weight. ##STR27##

POLYMERIZATION EXAMPLE X

The same procedure as in Polymerization Example I was repeated using7.15 g of the monomer M-I, 1.88 g of maleic anhydride and 4.90 g ofnorbornene along with 0.82 g of AIBN and 27.87 g of toluene. In result,the polymer represented by the following formula P10 was obtained at anamount of 8.36 g, which was measured to be 6,400 in polystyrene-reducedweight average molecular weight. ##STR28##

POLYMERIZATION EXAMPLE XI

The same procedure as in Polymerization Example I was repeated using4.77 g of the monomer M-I, 8.41 g of the monomer M-II synthesized inSynthesis Example II, and 4.90 g of maleic anhydride along with 0.82 gof AIBN and 36.16 g of toluene. In result, the polymer represented bythe following formula P11 was obtained at an amount of 11.57 g, whichwas measured to be 6,500 in polystyrene-reduced weight average molecularweight. ##STR29##

POLYMERIZATION EXAMPLE XII

The same procedure as in Polymerization Example I was repeated using3.57 g of the monomer M-I, 12.20 g of the monomer M-III synthesized inSynthesis Example III, and 4.90 g of maleic anhydride along with 0.82 gof AIBN and 41.35 g of toluene. As a result, the polymer represented bythe following formula P12 was obtained at an amount of 12.82 g, whichwas measured to be 6,000 in polystyrene-reduced weight average molecularweight. ##STR30##

POLYMERIZATION EXAMPLE XIII

The same procedure as in Polymerization Example VI was repeated using5.96 g of the monomer M-I, 7.06 g of the monomer M-VI synthesized inSynthesis Example VI, and 4.90 g of maleic anhydride along with 0.49 gof AIBN and 35.84 g of ethyl acetate. As a result, the polymerrepresented by the following formula P13 was obtained at an amount of11.29 g, which was measured to be 7,100 in polystyrene-reduced weightaverage molecular weight. ##STR31##

POLYMERIZATION EXAMPLE XIV

In 39.40 g of ethyl acetate, 4.77 g of the monomer M-I, 10.03 g of themonomer M-IX synthesized in Synthesis Example IX and 4.90 g of maleicanhydride were polymerized with the aid of 0.49 g of AIBN in 39.40 g ofethyl acetate in the same manner as in Polymerization Example VI, toallow 11.82 g of the polymer represented by the following structuralformula P14. It was measured to have a polystyrene-reduced weightaverage molecular weight of about 6,900. ##STR32##

POLYMERIZATION EXAMPLE XV

In 33.64 g of ethyl acetate, 11.92 g of the monomer M-I and 4.90 g ofmaleic anhydride were polymerized with the aid of 0.49 g of AIBN in33.64 g of ethyl acetate in the same manner as in Polymerization ExampleVI, to allow 9.42 g of the polymer represented by the followingstructural formula P15. It was measured to have a polystyrene-reducedweight average molecular weight of about 7,000. ##STR33##

RESIST FORMULATION AND ASSAY EXAMPLE I

100 weight parts of the resin P1 obtained in Polymerization Example Iwere dissolved, along with 1.6 weight parts ofdiphenyl(4-methylphenyl)sulfonium triflate and 0.04 weight parts ofmethyl ammonium hydroxide, in 500 weight parts of propyleneglycol methylether acetate (PGMEA) and the solution was filtered through a 0.2 μmmembrane.

The resist solution thus obtained was coated on a substrate by use of aspinner and dried at 110° C. for 90 sec, to form a coating 0.6 μm thick.This coating was exposed to light in an ArF excimer laser steper whilethe diphenyl(4-methylphenyl)sulfonium triflate and the methyl ammoniumhydroxide served as a photoacid generator and an acid diffusionpreventer, respectively, and then, baked at 130° C. for 90 sec.Subsequently, the exposed coating was immersed in an aqueous 2.38 wt %tetramethylammonium hydroxide solution for 60 sec for development,washed and dried to form a resist pattern.

With a sensitivity of 21 mJ/cm², the resist pattern was found to be goodin adherence to substrate and show a resolution of 0.15 μm.

The 0.2 μm line-and-space (L/S) pattern formed after the development,was observed with a scanning electron microscope to examine itsadherence to substrate. If bad conditions, such as released or loosestates, were found, the adherence to substrate was determined to be"poor"; if not found, the adherence to substrate was determined to be"good".

As far as sensitivity, when there was formed the 0.2 μm line-and-space(L/S) pattern in which the lines had an equal width, the exposure energyused was an optimal energy and was regarded as the sensitivity for thepattern. Also, a pattern dimension at which the pattern could beresolved as minimally as possible under the optimal energy, was definedas the resolution for the pattern.

EXAMPLES II TO IX

The resins obtained in Polymerization Examples II to IX were dissolvedin a solvent, along with a photoacid generator and a base additive, andfiltered through 0.2 μm membranes to produce resist compositions, asindicated in Table 1, below.

Using an ArF excimer laser steper (lens numerical aperture 0.60), theseresist compositions were formed into positive resist patterns which weretested as in Example I. The test results are given in Table 1, below.

                                      TABLE 1                                     __________________________________________________________________________    No.                 Properties                                                of  Composition (wt. parts)                                                                       Adher.                                                                             Sensitiv.                                                                          Develop                                                                            Resol'n                                    Exmp.                                                                             Resin                                                                             .sup.1 PAG                                                                       .sup.2 Base                                                                       .sup.3 Solvent                                                                     to Sub.                                                                            (mJ/cm.sup.2)                                                                      ability                                                                            (μm)                                    __________________________________________________________________________    II  P2(100)                                                                           1.4                                                                              0.03                                                                              460  good 16   good 0.13                                       III P3(100)                                                                           1.4                                                                              0.03                                                                              480  good 15   good 0.13                                       IV  P4(100)                                                                           1.4                                                                              0.03                                                                              480  good  1   good 0.14                                       V   P5(100)                                                                           1.4                                                                              0.03                                                                              460  good 14   good 0.14                                       VI  P6(100)                                                                           1.6                                                                              0.04                                                                              480  good 16   good 0.13                                       VII P7(100)                                                                           1.6                                                                              0.04                                                                              460  good 17   good 0.14                                       VIII                                                                              P8(100)                                                                           1.6                                                                              0.04                                                                              500  good 16   good 0.13                                       IX  P9(100)                                                                           1.6                                                                              0.04                                                                              460  good 19   good 0.14                                       __________________________________________________________________________     .sup.1 Photoacid generator: diphenyl(4methylphenyl)sulfonium triflate.        .sup.2 Base additive: methyl ammonium hydroxide.                              .sup.3 Solvent: propylene glycol methyl ether acetate (PGMEA).           

Observation was also done to examine the heat deformation of the resistpatterns after they were heated at 110° C. on a hot plate, leading tothe conclusion that nowhere were found deformed patterns and theirthermal resistance was superior.

EXAMPLE X TO XV

Positive resist patterns were formed from the compositions indicated inTable 2, below, in the same manner as in Example I, and assayed forvarious properties. The results are also given in Table 2.

                                      TABLE 2                                     __________________________________________________________________________    No.                 Properties                                                of  Composition (wt. parts)                                                                       Adher.                                                                             Sensitiv.                                                                          Develop                                                                            Resol'n                                    Exmp.                                                                             Resin                                                                              .sup.1 PAG                                                                       .sup.2 Base                                                                      .sup.3 Solvent                                                                     to Sub.                                                                            (mJ/cm.sup.2)                                                                      ability                                                                            (μm)                                    __________________________________________________________________________    X   P10(100)                                                                           1.6                                                                              0.04                                                                             480  good 24   good 0.14                                       XI  P11(100)                                                                           1.6                                                                              0.04                                                                             460  good 21   good 0.13                                       XII P12(100)                                                                           1.6                                                                              0.04                                                                             460  good 23   good 0.13                                       XIII                                                                              P13(100)                                                                           1.6                                                                              0.04                                                                             500  good 25   good 0.14                                       VX  P14(100)                                                                           1.6                                                                              0.04                                                                             500  good 24   good 0.14                                       XV  P15(100)                                                                           1.6                                                                              0.04                                                                             500  good 26   good 0.15                                       __________________________________________________________________________     .sup.1 Photoacid generator: diphenyl(4methylphenyl)sulfonium triflate.        .sup.2 Base additive: methyl ammonium hydroxide.                              .sup.3 Solvent: propylene glycol methyl ether acetate (PGMEA).           

EXAMPLES XVI TO XXIII

The resins, P2, P8, and P10 to P14, were dissolved, singly or incombinations, in a solvent, along with photoacid generators and baseadditives, and filtered through 0.2 μm membranes to produce resistcompositions, as indicated in Table 3, below.

Using an ArF excimer laser steper (lens numerical aperture 0.60), theseresist compositions were formed into positive resist patterns which weretested as in Example I. The test results are given in Table 3, below.

                                      TABLE 3                                     __________________________________________________________________________    No.                   Properties                                              of  Composition (wt. parts)                                                                         Adher.                                                                            Sensitiv.                                                                          Develop                                                                           Resol'n                                    Exmp.                                                                             Resin                                                                             .sup.1 PAG                                                                         .sup.2 Base                                                                       .sup.3 Solvent                                                                     to Sub.                                                                           (mJ/cm.sup.2)                                                                      ability                                                                           (μm)                                    __________________________________________________________________________    XVI P2(100)                                                                           A1/A2                                                                              B1  500  good                                                                              18   good                                                                              0.13                                               (1.4/0.4)                                                                          (0.05)                                                           XVII                                                                              P2  A1   B1/B2                                                                             500  good                                                                              12   good                                                                              0.14                                           (100)                                                                             (1.6)                                                                              (0.05)                                                           XVIII                                                                             P8  A1/A2                                                                              B1  500  good                                                                              16   good                                                                              0.13                                           (100)                                                                             (1.4/0.4)                                                                          (0.05)                                                           XIX P8  A1   B1/B2                                                                             500  good                                                                              13   good                                                                              0.14                                           (100)                                                                             (1.6)                                                                              (0.05)                                                           XX  P11/P10                                                                           A1   B1  460  good                                                                              18   good                                                                              0.13                                           (50/50)                                                                           (1.6)                                                                              (0.05)                                                           XXI P12/P10                                                                           A1   B1  460  good                                                                              21   good                                                                              0.13                                           (50/50)                                                                           (1.6)                                                                              (0.05)                                                           XXII                                                                              P13/P10                                                                           A1   B1  480  good                                                                              23   good                                                                              0.13                                           (50/50)                                                                           (1.6)                                                                              (0.05)                                                           XXIII                                                                             P14/P10                                                                           A1   B1  480  good                                                                              22   good                                                                              0.13                                           (50/50)                                                                           (1.6)                                                                              (0.05)                                                           __________________________________________________________________________     .sup.1 Photoacid generator: A.sub.1, diphenyl(4methylphenyl)sulfonium         triflate; A.sub.2, phenyl (4methoxyphenyl)iodonium triflate.                  .sup.2 Base additive: B.sub.1, methyl ammonium hydroxide; B.sub.2,            tributyl amine.                                                               .sup.3 Solvent: propylene glycol methyl ether acetate(PGMEA).            

Observation was also done to examine the heat deformation of the resistpatterns after they were heated at 110° C. on a hot plate, leading tothe conclusion that nowhere were found deformed patterns and theirthermal resistance was superior.

As described hereinbefore, the chemical amplification resistcompositions according to the present invention can be easily controlledin sensitivity by regulating the content and kind of the norbornenederivatives in the matrix polymers in addition to being superior inadherence to substrate and dry etch resistance. With these advantages,the chemical amplification resist compositions can be formed into resistpatterns much improved in transparency, photosensitivity and resolution.Consequently, the chemical amplification resist compositions of thepresent invention can be so useful in fabricating semiconductor devices,which are expected to be further miniaturized. Particularly, the resistcompositions are suitable to KrF and ArF excimer lasers, enabling asubmicrolithography process to be as exquisite as 0.2 μm or less.

Although the invention has been described in detail by referring tocertain preferred embodiments, it will be understood that variousmodifications can be made within the spirit and scope of the invention.The invention is not to be limited except as set forth in the followingclaims.

What is claimed is:
 1. A copolymer, represented by the following generalformula I: ##STR34## wherein, X is selected from the group consisting ofthe following general formulas II, III and IV: ##STR35## wherein R₁ isselected from the group consisting of straight or branched alkyl groups,cyclic or polycyclic alkyl groups, alkyl carbonyl groups, branched alkylcarbonyl groups, and cyclic or polycyclic alkyl carbonyl groups, allcontaining 1-10 carbon atoms; R₂, R₃ and R₄ are independently selectedfrom the group consisting of straight or branched alkyl groups, andcyclic or polycyclic alkyl groups, all containing 1-10 carbon atoms;andl, m, n and o each are a repeating number not more than 0.5,satisfying the condition that l+m+n+o=1 and 0.4≦o≦0.5.
 2. A copolymer asset forth in claim 1, wherein l and m each range from 0 to 0.5 with0.15≦l+m≦0.5 and n ranges from 0 to 0.35.
 3. A chemical amplificationresist composition, comprising;a copolymer represented by the followinggeneral formula I: ##STR36## wherein, X is selected from the groupconsisting of the following general formulas II, III and IV: ##STR37##wherein R₁ is selected from the group consisting of straight or branchedalkyl groups, cyclic or polycyclic alkyl groups, alkyl carbonyl groups,branched alkyl carbonyl groups, and cyclic or polycyclic alkyl carbonylgroups, all containing 1-10 carbon atoms; R₂, R₃ and R₄ areindependently selected from the group consisting of straight or branchedalkyl groups, and cyclic or polycyclic alkyl groups, all containing 1-10carbon atoms; and l, m, n and o each are a repeating number not morethan 0.5, satisfying the condition that l+m+n+o=1 and 0.4≦o≦0.5; aphotoacid generator; and a solvent.
 4. A chemical amplification resistcomposition as set forth in claim 3, wherein the photoacid generator isat least one selected from the group consisting of onium saltscomprising triphenylsulfonium triflate, triphenylsulfoniumhexafluoroantimonate, diphenyliodonium triflate, diphenyliodonium methylbenzene sulfonate, and the compounds represented from the followingformulas XI and XII: ##STR38## wherein R₁ and R₂, which may be the sameor different, each represents an alkyl, an allyl or an aryl; R₃ and R₄,which may be the same or different, each represents a hydrogen atom, analkyl or an alkoxy; and n is an integer of 0-14; halogen compoundscomprising 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane,phenyl-bis(trichloromethyl)-triazine andnaphthyl-bis(trichloromethyl)-triazine; diazoketone compounds comprising1,3-diketo-2-diazo compounds, diazobenzoquinone compounds anddiazonaphthoquinone compounds; sulfone compounds; sulfonic acidcompounds; and nitrobenzyl compounds.
 5. A chemical amplification resistcomposition as set forth in claim 3, wherein the photoacid generator isused at an amount of approximately 0.3-10 weight parts based on 100weight parts of the copolymer and the base additive is used at an amountof approximately 0-50 weight parts based on the 100 weight parts of thephotoacid generator.